1. Field of the Invention
This invention relates to an improved thin magnetic layer and a method of manufacture therefor. More particularly, the invention is an abrasion resistant, single phase composition of nickel-iron and aluminum oxide, and its preparation by cosputtering. The single phase composition is suitable for use in magnetic head pole piece applications.
2. Description of the Relevant Art
It is desirable for materials used in magnetic head pole piece applications to have specific mangetic and mechanical properties. High permeability and low coercivity are desired to maximize magnetic performance of the head. High abrasion resistance is desired to prevent degradation of the magnetic properties through frequent frictional contact with magnetic media. Internal stress is another important mechanical property of the magnetic layer. High tensile or compressive internal stresses of the magnetic layer can cause a loss of mechanical integrity, such as by buckling, cracking, or a loss of adhesion to the underlying magnetic head substrate. It is also desirable that the materials used be capable of easy manufacture. For example, the cost of manufacturing a thin magnetic layer is reduced if it can be deposited in a single in situ process as opposed to a series of deposition steps. Manufacturing costs are also reduced if the materials used can be etched in a single in situ process to allow for easy patterning into a pole piece. Magnetic head pole pieces have been manufactured from several materials, each material having specific drawbacks.
It is known that magnetic head pole pieces can be manufactured from alloys of nickel and iron (hereinafter referred to as NiFe). Although NiFe generally exhibits adequate magnetic properties, it has been found to be susceptible to abrasion from contact with magnetic media and hence lacks durability when used in pole piece applications. Several modifications of NiFe have resulted in increased abrasion resistance.
One such modification of NiFe is the addition of aluminum oxide (hereinafter referred to as Al.sub.2 O.sub.3) in the form of a layer. More specifically, the pole piece is formed from a laminate of alternating layers of NiFe and Al.sub.2 O.sub.3. The layers are formed on the magnetic head substrate by either evaporative deposition or sputter deposition. These laminated structures yield pole pieces exhibiting some improvement in wear resistance and magnetic properties compared to magnetic layers manufactured solely from NiFe. However, the laminated structure exhibits little significant improvement in the internal stresses of the magnetic layer and is not easily manufacturable into a pole piece. The layered structure is not capable of easy patterning by an in situ etching process because the alternating layers of NiFe and Al.sub.2 O.sub.3 require different etchants. Also, the layered structure is difficult to deposit since alternating layer depositions are required.
It has also been proposed to modify NiFe by mixing together particles of NiFe and Al.sub.2 O.sub.3 and forming them into a magnetic layer by high temperature sintering and then rolling. The magnetic layer is then bonded to the magnetic media head. Although the resulting magnetic layer exhibits some improvement in wear resistance compared to layers made solely from NiFe, this technique is not applicable to the manufacture of thin films.
It is therefore desirable to create a thin magnetic layer and a method of manufacture thereof resulting in improved abrasion resistance without degradation of magnetic properties. In addition, it is desirable that the magnetic layer have the aforementioned characteristics of internal stress and easy manufacturability.